1. Field of the Invention
The invention relates to evaporators and more particularly to a system for avoiding shocks which can result from flooding of evaporators of the type having bottom steam inlets.
2. Description of the Prior Art
There are advantages to introducing steam into an evaporator through an inlet located at or near the bottom of the evaporator. The use of bottom steam inlets for both plate-type and tube-type evaporators is known. However, use of such a bottom steam inlet entails a potential operating problem.
As the heating steam condenses within the evaporator, the condensate flows downward, and is removed. If condensate is not removed as fast as further condensate is produced by condensation of the steam which enters the evaporator, the level of condensate will rise. This condition can result from any kind of failure in the condensate removal system, such as a malfunction in a pump or control valve. When the condensate level becomes too high, steam entering the evaporator will be condensed while submerged in the condensate, causing condensation shock or water hammer.
Under some conditions such shock or water hammer can be very severe, causing very substantial damage to the surrounding heating surface, regardless of the surface's structure, whether plate or tubular. It is imperative that an evaporator not be operated under these conditions for any extended period.
No reliable and economically reasonable solution for this problem has been available.